To place an entrance in the fence, use barrier=gate etc. (see list of documented values) on a node of the way (or, less commonly, on a micromapped segment of the fence).

Fence or wall

The Wikipedia page for Fence notes that "a fence differs from a wall in not having a solid foundation along its whole length."

The page for Wall leaves the distinction more open with "The conventional differentiation is that a fence is of minimal thickness and often open in nature, while a wall is usually more than a nominal thickness and is completely closed, or opaque. More to the point, an exterior structure of wood or wire is generally called a fence—but one of masonry is a wall."